The present invention relates generally to the formation of thin metallic silicide films on silicon substrates, and more particularly to the formation of such films on the surface of heated silicon substrates by ion beam deposition.
Metallic silicides have been found to be useful for providing conducting layers or interconnects in the formation of integrated circuits due to their low resistivity, resistance to electromigration and high thermal stability. Films or very thin coatings of metallic silicides have been particularly useful for providing gates and interconnects in shallow junction technology due to the low sheet resistance of the metallic silicide films.
The primary techniques previously used for preparing thin metallic silicide films on semiconductor substrates include physical vapor deposition procedures practiced by cosputtering with separate metal and silicon targets or by sputtering from a single silicide target have been used to form the films. Metallic silicide films have also been deposited by chemical vapor deposition or by depositing a thin metal film of high purity onto a silicon substrate and then thermally reacting the metal-silicon couple to form the metallic silicide.
These previously known techniques provide for the formation of various metallic silicide films or layers on silicon and other type substrates. However, there are several shortcomings and drawbacks which detract from the usefulness of these previously known metallic silicide-film forming techniques. For example, the purity of the film deposited onto the substrate surface was limited by the purity of the starting materials. Any impurities present in the sputter-targets or the deposition gases were incorporated directly into the film. These impurities resulted in the films having relatively high intrinsic resistivity. Another problem attendant in the practice of the previous techniques is that the films had to be annealed at relatively high temperatures (e.g. about 800.degree. C. for titanium disilicide films) in order to lower the resistivity of the films to acceptable levels. Such annealing of metallic silicide films on silicon substrates containing electronic grade n- or p-type dopants caused considerable dopant diffusion and volatilization which resulted in significant degradation and/or alteration in the properties of the metallic silicide-coated article.